It has long been known that the hot drawing of an acrylic fibrous material is capable of beneficially enhancing the tensile properties thereof through molecular orientation. Drawing or stretching acrylic fibrous materials accordingly commonly is practiced prior to most fiber end use applications.
During the initial formation of an acrylic multifilament fibrous material complete filament size uniformity is difficult to achieve. Upon subsequent drawing broken filaments within the multifilament fibrous material are commonly observed at least some of which may be traced to filament size diversity. Such broken filments have an adverse influence upon process stability during the hot drawing operation. For instance, a broken filament during passage through the drawing zone may become wound upon a roll to form a roll wrap which requires a shut down of the drawing operation to eliminate the same. The uniform quality of the product is accordingly reduced. Productivity is diminished and labor costs are increased.
Heretofore, those interested in improving the stability of hot drawing operations have concentrated primarily upon various mechanical refinements of the drawing equipment involved. Rollers present in the drawing zone may be provided with a matte finish rather than a highly polished finish. Devices have been employed in association with the rollers to remove filaments which tend to adhere to the same, e.g. doctor blades, brushes, compressed air jets, etc. Additionally, various dressings for the fibrous material have been proposed wherein a continuous coating is applied to the same.
When an acrylic fibrous material is intended for use as a precursor in the formation of a carbonaceous fibrous material via thermal processing, it is particularly advantageous that the fibrous material uniformly possess a high degree of molecular orientation which may be difficult to reliably impart to the same employing standard drawing technology particularly when the fibrous material is substantially untwisted and consists of thousands of individual filaments.
In my commonly assigned U.S. Pat. No. 3,508,874 entitled "Production of Carbon Yarns" is disclosed an improved process for the thermal stabilization and carbonization of an acrylic fibrous material. The fibrous material which undergoes processing in the process described therein is preferably highly molecularly oriented. See, also, commonly assigned U.S. Pat. No. 3,539,295 of Michael J. Ram for an additional representative process for the thermal conversion of an acrylic fibrous material to a carbonaceous fibrous material.
It is an object of the invention to provide an improved process for the drawing of a continuous length of an acrylic multifilament fibrous material.
It is an object of the invention to provide an improved process for the drawing of a continuous length of an acrylic multifilament fibrous material which is carried out on a continuous basis in an efficient manner under highly stable operating conditions.
It is an object of the invention to provide an improved process for the drawing of a continuous length of an acrylic multifilament fibrous material wherein the individual filaments thereof are uniformly drawn and the frequency of filament breakage commonly observed during the drawing of a multifilament fibrous material is substantially reduced.
It is an object of the invention to provide an improved process for the drawing of a continuous length of an acrylic fibrous material which produces a drawn fibrous product of improved quality.
It is a further object of the invention to provide an improved process for the drawing of an acrylic multifilament fibrous material which yields a drawn product which particularly is suited for subsequent thermal stabilization and carbonization to form a carbonaceous fibrous material.
These and other objects as well as the scope, nature, and utilization of the improved process will be apparent from the following detailed description and appended claims.